Hi Geoff,
I have finally been able to test the patched version under some proper
load. I was using tsung (http://tsung.erlang-projects.org/). I recorded
a browser session in which I accessed a couple of pages, then tried to
replay it with tsung.
It looks like there is a memory leak in the patched version because the
virtual memory size grew at a constant pace until eventually varnishd
filled up the whole available space. I tried exactly the same scenario
with an unpatched trunk (same revision that I applied the patch to) and
it worked fine. Note there were no stale objects or conditional requests
during the test because I set ttl to a high value so it's either a hit
or a miss for an uncacheable object.
I have a rather complex setup which includes apache with mod_proxy_html
which I use to reverse proxy a real Internet web site
(www.telegraph.co.uk). If there is anything I can do to help you
diagnose the problem, please let me know.
On 09/03/2011 10:57, Geoff Simmons wrote:
Hello again,
And yet another version (v5) of the patch for conditional backend
requests. Like the last version, this is one is to keep pace with recent
commits to the trunk. The patch applies to:
commit 13c60b522a6c7abe9cc1052c2a244f25f2ba5227
Date: Tue Mar 8 14:47:57 2011 +0100
phk committed some changes related to this feature, mainly the addition
of the new timer variable to VCL. There are also some changes in the way
that previous version of the patch worked.
- The name of the timer for conditional requests changed again, now to
"keep". The management parameter is "default_keep".
- In addition to beresp.keep, obj.keep and stale_obj.keep, there is now
req.keep, which sets an upper bound for the keep time within a session.
(Like req.ttl, which phk added yesterday.)
- The keep interval now begins after ttl and grace have elapsed, so an
object is available for conditional requests after obj.ttl + obj.grace,
and is scheduled for eviction after obj.ttl + obj.grace + obj.keep. (In
previous versions of the patch, the keep interval began after ttl
elapses, independent of grace, and object were evicted after obj.ttl +
max(obj.grace, obj.keep).)
- The default value default_keep is now 0, so you need to set a non-zero
default_keep, or set keep in VCL, to make the conditional requests happen.
The Wiki page has been updated to reflect all of this:
http://www.varnish-cache.org/trac/wiki/BackendConditionalRequests
@phk: I made one change in the commits from yesterday. Since
default_keep = 0 and EXP_get_*() was returning -1 for any timer = 0,
*.keep was always -1 unless it was changed in VCL. I think VCL authors
wouldn't expect that; I got feedback about an earlier version in which
beresp.keep was -1 after a backend validation, which both the reporter
and I thought was wrong, so I fixed it in the next version.
Now I have this in cache_expire.c:
double \
EXP_Get_##fld(const struct exp *e) \
{ \
- return (e->fld> 0. ? e->fld : -1.); \
+ return (e->fld> 0. ? e->fld : 0.); \
} \
This required a change in test case b00040.vtc, which expects req.grace
== -1, but that doesn't seem to be a critical value there.
Best,
Geoff
Best regards,
--
Dmitry Panov
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